Process for improving cellulose textile material by alkaline treatment

ABSTRACT

CELLULOSE TEXTILE MATERIAL IS TREATED WITH A SOLUTION HAVING A HIGH CAUSTIC SODA CONCENTRATION OF 25-35% AT ROOM TEMPERATURE IN THE FIRST STEP, AND THEREAFTER IS TREATED WITH A SOLUTION OF A LOW CAUSTIC SODA CONCENTRATION OF ABOUT 10% AT ROOM TEMPERATURE IN THE SECOND STEP, AND THEREBY THE CELLULOSE TEXTILE MATERIAL SWELLS MUCH MORE THAN CONVENTIONAL ONE-STEP TREATMENT WITH A CAUSTIC SODA SOLUTION. IF THE ABOVE TWO-STEP METHOD IS USED WITHOUT TENSION, THE STRETCHABILITY, MOISTURE ADSORPTION AND DYEING CAPACITIES OF THE CELLULOSE TEXTILE MATERIAL WILL BE IMPROVED; IF WITH TENSION, ITS LUSTER AND STRENGTH WILL BE IMPROVED.

Patented Feb. 2, 1971 3,560,139 PROCESS FOR IMPROVING CELLULOSE TEXTILEMATERIAL BY ALKALINE TREATMENT Toshihiko Snminokura, Yojuro Kyogoku, andKazuo Sekiguchi, Neyagawa, Japan, assignors to Kurashiki Spinning Co.,Ltd., Kurashiki, Japan, a corporation of Japan Filed Aug. 18, 1967, Ser.No. 661,564 -Claims priority, application Japan, Sept. 6, 1966, 41/59,072 Int. Cl. D06m N10 US. Cl. 8-125 4 Claims ABSTRACT OF THEDISCLOSURE Cellulose textile material is treated with a solution havinga high caustic soda concentration of 35% at room temperature in thefirst step, and thereafter is treated with a solution of a low causticsoda concentration of about 10% at room temperature in the second step,and thereby the cellulose textile material swells much more thanconventional one-step treatment with a caustic soda solution.

If the above two-step method is used without tension, thestretchability, moisture adsorption and dyeing capacities of thecellulose textile material will be improved; if wit htension, its lusterand strength Will be improved.

This invention relates to a process for improving cellulose textilematerial characterized in that it is successively treated with separatealkaline solution of different concentrations controlled in a specialmanner.

An object of the present invention is to provide a process for treatingcellulose textile material in such a manner as to make it highlystretchable.

Another object is to provide a process for imparting splendid luster tocellulose textile material, and thereby imparting a lustrous silkyappearance thereto.

Another object is to provide a process for imparting an increasedbreaking strength to cellulose textile material.

Another object is to provide a process for imparting an improvedmoisture adsorption to cellulose textile material.

Another object is to provide a process for imparting an improved dyeingcapacity to cellulose textile material.

Still another object is to provide a process for profitably achievingthe objects hereinabove described on a commercial basis.

Accompanying drawings are graphs showing the effects of some embodimentsof the present invention.

FIG. 1 is a graph showing the lateral swelling of a cotton single fiberin a caustic soda solution according to the process of the presentinvention, as compared with that of another cotton single fiber treatedaccording to the conventional method.

FIG. 2 is a graph showing the percent shrinkage of cotton single fibershrunk in a caustic soda solution, as in FIG. 1, according to theprocess of the present invention, as compared with those of anothercotton single fiber treated according to the conventional method.

FIG. 3 is a graph showing comparative percent shrinkage of a series of28/ 2s cotton yarn when each of them is treated with a caustic sodasolution of a certain concentration different from one another in thefirst step, and thereafter is also treated with a caustic soda solutionof a definite concentration in the second step.

A process for treating cellulose textile fibers With an alkalinesolution has been well-known as mercerization since Mercer was granted apatent on his invention in 1843. Also Lowe was granted, in 1 889, apatent on his invention regarding a process for washing cellulosetextile fibers with tension by means of water after their alkalinetreatment. This process has been well-known also as mercerization andgenerally employed ever since. Lowes patent relates to a process ofmercerization with tension, and has been of much practical use as aprocess of imparting a silky appearance to cotton, the so-called silketcotton. Quite recently another process, which is usually called slackmercerization has attracted much attention. This process consists intreating cotton textile fibers with an alkaline solution without tensionso as to impart stretchability to the cotton textile fibers by makinguse of their shrinking during the treatment.

Each of these processes depends on the fundamental principle of treatingcotton textile fibers with an alkaline solution: slack mercerizationproviding a stretchable cotton; mercerization with tension, a silketcotton. Both processes make use of the properties of cellulose textilefibers to swell when immersed in an alkaline solution and therebyproduce a certain looseness in their molecular structure, especiallytheir molecular orientation and crystallinity.

A process of slack mercerization makes use of the properties ofcellulose textile fibers to swell on treating in a lateral direction andshrink in a longitudinal direction; a process of mercerization withtension makes use of an improvement of surface luster of the cellulosetextile fibers brought about both by the surface smoothness resultingfrom swelling on treating and by improved rearrangement of theirmolecular structure so as to bring about a satisfactory orientationresulting from stretching fibers under above-mentioned loose molecularstructure. In order to improve the effects of the treatment, therefore,it is apparent that in either case it is necessary to improve the degreeof swelling of the cellulose textile fibers when they are treated withan alkaline solution and thereby causing a looseness in the molecularstructure.

Generally, in treating cellulose textile fibers with an alkalinesolution, as for example with caustic soda, their maximum degree ofswelling will be obtained when the concentration of the caustic soda isabout 18%. It cannot be said, however, that even such a maximum degreeof swelling is not enough for either imparting stretchability to thefibers as a result of their longitudinal shrinkage or imparting highlysilky appearance to the fibers as a result of their improved surfacesmoothness and molecular orientation.

Various expendients have been proposed previously to improve the degreeof swelling in order to overcome the aforementioned difiiculties, thatis, the difficulties attributable to insufficient swelling. Thus, it hasbeen proposed to scour cellulose textile fibers well in order to removeimpurities out of the surfaces of the fibers. It has also been proposedto rub away the primary wall of cotton which restricts swelling. But itis too expensive to scour well; it is impossible to remove the primarywall by polishing it on a large commercial scale even if it may bepossible experimentally. So neither of these expedients has been foundto be practical.

As a result of laborious research concerning this matter, however, wehave now succeeded in overcoming the aforementioned difficulties. Inaccordance with the present invention, cellulose textile fibers arefirst treated with a solution having a high caustic soda concentrationof 25 35% at room temperature in the first step, and thereafter aretreated with a solution having a low caustic soda concentration of about10% at room temperature in the second step, and thereby the degree ofswelling of the cellulose textile fibers are increased to a markeddegree.

If this two-step method is adapted and if cellulose textile fibers aretreated without tension, their stretchability, moisture adsorption anddyeing capacities will be improved. Or if the cellulose textile fibersare treated with tension, their luster and strength will be increased.Based on this principle, it is easy to bring into practice an effectivetreatment of improving the stretchability, luster or other properties ofcellulose textile material on a large commercial scale at low cost.

FIG. 1 shows a swelling effect of a cellulose textile fiber on treatingby means of a caustic soda solution according to the present invention.The curve B shows, by way of comparison with the present invention, therelationship between the degree of swelling of the cellulose textilefiber by means of a caustic soda solution at room temperature and theconcentration of the caustic soda solution according to the conventionalmethod. The swelling of the cellulose textile fiber is greatest when theconcentration of the caustic soda solution is about 18%. The degree ofswelling at this time is 136%.

After the cellulose textile fiber is treated with a solution having ahigh caustic soda concentration of 32% in the first step, the fiber isagain treated with different solutions having different caustic sodaconcentration in the second step. The curve A shows the degree ofswelling in this case. The maximum degree of swelling is 141% when theconcentration of the caustic soda of the second step is 10%. Hence FIG.1 shows clearly that the degree of swelling in the curve A is muchgreater than that in the curve B, that is, the present inventionincreases the degree of swelling much more than the conventional method.

Now consider the action of an alkaline solution on cellulose textilefibers.

Generally, it is assumed that a chemical combination takes place betweencellulose textile fibers and a caustic soda solution and forms amolecular complex of cellulose and caustic soda. This is called thealkali cellulose. It is said that at room temperature alkali cellulose Iis produced when the concentrations of caustic soda solutions are12-22%; alkali cellulose 11 when the concentrations are 25% or over.

Alkali cellulose I has better hydration capacity and 1 swelling thanalkali cellulose II. In order to increase the swelling of cellulosetextile fibers, therefore, it is necessary to permit the cellulosetextile fibers to become the structure of alkali cellulose I, and tomake it absorb much more water so as to increase lateral swelling.

In the present case, cellulose textile fibers are first treated with asolution having a high caustic soda concentration so as to producealkali cellulose II. By immersing the sample in a caustic soda solutionof about 10% concentration, its structure will become similar to that ofalkali cellulose I having a great hydration capacity. What is more,concentration difference of caustic soda solutions between inside andoutside of the cellulose fibers will rapidly become greater at this verymoment, which gives rise to osmotic pressure. These phenomena make thefibers absorb greater quantity of water, increase its hydration capacitystill greater and bring about a highly swelling condition. Thus highlyhydrated alkali cellulose composed of alkali, water and cellulose isformed. We can see that in the caustic soda treatment of the second stepthe optimum condition is obtained when the solution has a concentrationof 10% at room temperature (FIG. 1).

Now consider the test results of slack mercerization to which a two-steptreatment with a caustic soda solution is applied. In FIG. 2 the curve Bshows the percent shrinkage of a cotton single fiber treated by theconventional method with respect to caustic soda solution havingdifferent concentrations. And the curve A shows the percent shrinkage ofa cotton single fiber which was treated, as mentioned above, with asolution having a caustic soda concentration of 31.2% in the first stepand then treated with a solution having different concentration in thesecond step.

A comparison of the curve A with the curve B shows that with theconventional method maximum percent shrinkage was only 13% when theconcentration of the caustic soda solution was about 18% while with themethod of the present invention maximum percentage was 22%. The methodof the present invention was as follows: The cotton single fiber wastreated with a solution having a caustic soda concentration of 31.2% inthe first step and then was treated again with a solution having acaustic soda concentration of 10%. These were the results of testsconducted on a cotton single fiber. But similar results were obtainedwith respect to other cellulose fibers.

Generally, it is said that the shrinking of cellulose textile fibers bymeans of a caustic soda treatment without tension is caused by theshrinking of the fibers in a direction of their lengths resulting fromthe swelling of the fibers in a direction of their widths. In the caseof a yarn, however, its percent shrinkage becomes greater because of thecombined effects of swelling and shrinking of a single fiber treated andof the twisting of the fiber and of the yarn. In the case of a fabric,its shrinking is caused by aforementioned conditions interacting oneanother in a complicated manner.

Now consider the results of tests on cotton yarn. A 28/ 2s cotton yarnwas treated with different solutions having different caustic sodaconcentrations in the first step and thereafter the yarn thus treatedwas treated with 10% caustic soda solution. In such a treatment it wasfound that when the concentration of the caustic soda solution was about30% in the first step, the percent shrinkage of the yarn was mosteffective, which was about 34% as may be seen from FIG. 3.

What we have described above is a case in which the shrinking waseffected without tension. Now we will describe a case in which theprocess of the present invention was applied to mercerization withtension.

As has been described before, cellulose textile fibers were treated with31.2% caustic soda solution in the first step and were immersed in about10% caustic soda solution to swell the fibers to the fullest extent andtreated with tension (or treated with tension while the fibers are in aswollen condition). Then it was neutralized, washed with water, anddried.

As may be seen from the examples to be described hereinafter, the yarnor the fabric so obtained had a better luster, stronger strength, betterdyeing and absorption capacities than the corresponding yarn or fabrictreated by the conventional method.

As has been described above, in treating cellulose textile fibers withan alkaline solution, the present invention provides a process to treatthe fibers with a solution having such a caustic soda concentration asto form alkali cellulose II in the first step, and then to treat themagain with a solution having a caustic soda concentration of 10% in thesecond step so as to swell the fibers to the fullest extent.

By so doing, the process of the present invention is capable ofimproving a slack mercerization effect by increasing the percentshrinkage of the fibers in a treatment without tension, and also iscapable of improving a mercerization effect by increasing the luster ofthe fibers in a treatment with tension.

What is more, in the case of slack mercerization, dyeing and adsorptioncapacities of the fibers are also improved; in the case of mercerizationwith tension, the breaking strength, dyeing and adsorption capacities ofthe fibers are also increased. A treating effect of cellulose textilematerial can be markedly improved by a process which can be easilybrought to practice on a commercial basis. So the present invention hasan important bearing on the utilization of the natural fibers, and sohas an excellent effect.

Cellulose textile material may be treated according to the process ofthe present invention in the form of fibers, yarn or fabrics.

Now some embodiments of the present invention will be described indetail.

EXAMPLE 1 A 28/2s scoured cotton yarn was hanked with a diameter of 50cm. The yarn was treated with 30% caustic soda solution without tensionat room temperature for 3 minutes, and the caustic soda solution waslightly removed centrifugally from the surface of the yarn.

Next, the yarn was treated again with 10% caustic soda solution for 3minutes, and the caustic soda solution was lightly removedcentrifugally, neutralized in 0.2% acetic acid solution, washed withwater, and dried. Then the yarn thus obtained was shrunk to a hank witha diameter of 31 cm.

Then, the yarn was treated with 3% melamine formaldehyde precondensate(0.3% acid catalyst) solution, removed said solution centrifugally fromthe surface thereof, pre-dried at 60 C., and cured at 150 C. for 3minutes. The resultant yarn had much better stretchability and muchimproved adsorption and dyeing capacities. stretchability than thecorresponding yarn or fabric treatby the process of the presentinvention is better in its stretch-ability than the corresponding yarnor fabric treated by the conventional method, as shown in FIGS. 1 and 2.Furthermore, its dyeing and adsorption capacities are also excellent.

EXAMPLE 2 A 30/2s scoured ramie yarn (in cotton counts) was used. Theramie yarn was treated in the same manner as described in Example 1.Percent shrinkage of the ramie yarn was 50%, which was greater than thatof the cotton yarn. As compared with the cotton yarn, the ramie yarn wasbetter in its stretchability. What'is more, the breaking strength,adsorption and dyeing capacities of the ramie yarn were also excellent.

EXAMPLE 3 In the first step a 28/2s pure cotton yarn was first treatedwith 30% caustic soda solution at room temperature for 3 minutes and thecaustic soda solution was removed ceutrifugally from the surface thereofin accordance with the process of the present invention. In the secondstep, the cotton yarn was treated with 10% caustic soda solution withtension while making it swell under wet condition. Such a tension wasapplied for 3 minutes at 30 C. to the cotton yarn as to make it longerthan the length of the yarn before its treatment. Then the yarn wasneutralized with 0.2% acetic acid solution, and washed with water.

For the sake of comparison, a yarn was treated with 15% caustic sodasolution; another yarn, in 18% caustic soda solution; and both yarnswere treated with tension by the conventional mercerization withtension. Then, 5 inspectors experienced in luster testing were asked toarrange the above-mentioned 3 kinds of yarns in the order ofsatisfactory luster according to their judgment by visual sensation.Table 1 shows such results.

TABLE 1 Swell- Order of judgment ing on by different treatinspectors*ing, Methods of treatments percent A B C D E Treated with 30% causticsoda solution, and then treated with 10% caustic soda solution withtension 141 1 1 2 1 1 Treated with 18% caustic soda solution withtension 136 2 2 1 2 3 Treated with 15% caustic soda Solution withtension 135 3 3 3 3 2 *The numeral 1 indicates the best quality; 2, thenext best quality;

and 3, the worst quality.

As may be seen from Table 1, the treatment in accordance with theprocess of the present invention will give much more excellent luster tocellulose textile material than the treatment in accordance with theconventional method. As has been described before, this is due to thefact that, by the swelling of the cellulose textile material to thefullest extent, molecules are re-arranged easily and satisfactorilywhile it is being treated with tension.

Table 2 shows the test results of the breaking strength As shown inTable 2, a mercerized cellulose textile material treated in accordancewith the process of the present invention was better in its breakingstrength than the corresponding product treated by the conventionalmethod. This is due to the following reasons: When the cellulose textilematerial is treated according to the process of the present invention,the fibers swell so well that their defects are much diminished and thattheir stress is distributed more or less uniformly. What is more, as thefibers are treated under tension when they are in a fully swollencondition, molecules are re-arranged, easily and fully, in a directionof fiber axis. Furthermore, the cellulose textile material treatedaccording to the process of the present invention has excellent dyeingand adsorption capacities. And so it may be said that from any viewpointit makes an important contribution to the textile field as a process ofmercerization. Having described the general nature of the invention andhaving illustrated its operation and advantages by specific examples,the invention is particularly pointed out and claimed in the appendedclaims.

We claim:

1. A process for improving cellulosic textile material comprising afirst step of treating the cellulosic material without tension with asolution containing 25 to 35% caustic soda at room temperature for about1 to 10 minutes to thereby produce alkali cellulose II, thereaftertreating the cellulosic textile material With a solution containingabout 10% caustic soda at room temperature for about 1 to 10 minutes tothereby produce alkali cellulose I, neutralizing the textile niaterial,washing the textile material with water and thereafter drying thetextile material.

2. A process according to claim 1 wherein the textile material is placedin tension when treated with the solution containing about 10% causticsoda.

3. A process for improving natural cellulose textile materialscomprising a first step of treating natural cellulosic material withouttension with a solution containing 25 to 35% caustic soda at atemperature of 15 to 30 C. for 1 to 10 minutes, removing excess causticsolution from the textile and thereafter treating the cellulose textilematerial without tension with a 25-35% caustic soda solution at atemperature of 15 to 30 C. for 1 to 10 minutes, removing the excesscaustic soda solution from the cellulose textile material, neutralizingthe textile material, washing the textile material and thereafter dryingthe textile material.

4. A process according to claim 3 wherein the natural cellulosicmaterial is held under tension and then treated with a solutioncontaining about 10% caustic soda at a temperature of 15 to 30 C. for 1to 10 minutes.

References Cited UNITED STATES PATENTS GEORGE F. LESMES, PrimaryExaminer 0 J. R. MILLER, Assistant Examiner US. Cl. X.R. 8127

